Project Summary/Abstract Pseudomonas aeruginosa (P. aeruginosa) is a Gram-negative, opportunistic pathogen associated with bacterial keratitis, especially in contact lens usage. With the increasing incidence of antibiotic resistance, our goal is to determine the role of the pro- inflammatory neuropeptide, Substance P (SP) and the anti-inflammatory neuropeptide, vasoactive intestinal peptide (VIP) in regulation of inflammation, innate immunity and restoration of corneal homeostasis. The aims of this proposal are: 1) to test the hypothesis that VIP modulates TLRs and TLR-related adaptor molecules; down- regulates the expression of adhesion molecules, decreases the migration/persistence of inflammatory cells (PMN, M, Langerhans cells) in the infected cornea; and promotes restoration of corneal homeostasis and re-modeling of the ECM, 2) to test the hypothesis that SP exacerbates disease pathogenesis through the up-regulation of TLRs and TLR- related adaptor molecules; up-regulates adhesion molecule expression and enhances the migration/persistence of inflammatory cells (PMN, M, Langerhans cells) in the infected cornea and degradation of the ECM. Experiments will include use of techniques such as real-time RT-PCR, short interfering RNA (siRNA), as well as plate counts, enzyme linked immunosorbant assay (ELISA), myeloperoxidase assay (MPO) for neutrophil (PMN) quantitation, dual antibody immunostaining, histopathology, and Western blotting. Our findings will be particularly significant for development of novel therapeutics for bacterial keratitis, targeting not only regulation of corneal infection and inflammation, but also the critical aspect of promoting tissue repair. Since in the United States alone the incidence of microbial keratitis is 25,000-30,000 cases annually with cost of treatment estimated at $15-30 million, the studies are relevant to human health and have considerable medical and economic impact.